To identify columns with constant value from particular table

I want to find column having same value in all rows for it. For e.g.
If table is as follows:
VAL FREQ PCT_CUM GRP AVG_VAL
10 20 100 10 1111
20 80 80 10 1111
30 50 100 20 1111
40 10 10 20 1111
50 40 50 20 1111
As, here you can see, AVG_VAL is column having constant value across all rows which is 1111.
Now my out put should be AVG _VAL 1111.
This way I need to find all columns having constant value and their values.
Now, currently I've written a code where I'm fetching every column from user_tab_columns for that particular table in for loop and then passing every column to following query:
SELECT COUNT(col_name)
FROM table_name
GROUP BY col_name
HAVING COUNT(col_name) = (SELECT COUNT (1) FROM table_name);
The query is created and executed dynamically
Is there any way tht I can do this in one query and avoid for loop? Plz. let me know